12. Properties

Every item (e. g. atom) can have a (virtually) random amount of properties. A property is a boolean value for each item, which can be either true (set) or false (not set). Each property has a unique name.

Some properties have a special meaning to the program. The user should not try to use them for anything else but for the intended purpose:

all: Always set for all items. The user should never try to modify this property, otherwise there may be unpredictable effects.
visible: True for all atoms, bonds, distances and primitives that have their display attributes set in a way to make them visible. It is maitained by the program, and should not be modified by the user. It is convenient for selecting only visible items.
selected: Set for all selected items. This property is modified by the methods explained in chapter "Selection" on page 12 , most commands act on items that have this property set.
displayed: Only items that have this property set will be visible. Setting it to false can be used to make items invisible.
movable: Only molecules that have this property set will be modified by interactive manipulations. Setting this property to false for part of the molecules can be used for moving molecules relative to each other.

Some properties are predefined and are calculated whenever a molecule is loaded. They are stored in the file setup/PropDef of the MOLMOL installation directory.

The user can define additional properties by using the DefProp* (e. g. DefPropAtom) commands. This is useful for simplifying the expressions used for selections. Also some commands take property names as arguments, the user can either use one of the predefined properties there, or one defined with DefProp*. Consult the online manual page of the DefProp* commands for examples of defining and using properties.